The abdomen usually lacks
scales, save for some in front of the pelvic fins and just behind the gill
membrane isthmus (a narrow strip of tissue).

There are 20 to 21 gill
rakers and generally 3 or 4 preorbital pores on either side of the head.

The male Pupfish have
dorsal and anal fins that are black.

General
information:

The Pecos pupfish
can usually be found and seems to thrive in saline bodies of water that
contain a limited number of other fish species. It occasionally lives in
fresher waters, but that is uncommon in such habitats. In the saline habitats,
populations can be very dense. Along the Pecos River, this pupfish
has most often been found in backwater areas and side pools that do not
have sunfish or other various other predators.The Latin name for
the Pecos Pupfish is Cyprinodon pecosensis.
The name Cyprinodon
translates carp tooth, or teeth like a carp.
Pecosensis
just referrs
to the geographic area in which the fish lives.

Observations
from the Fort Worth Zoo....The
pupfish tank can be seen in the Mountains and Deserts section of the Texas
Wild! exhibit.The fish are being bred to maybe someday help
to replenish areas of west Texas. Pecos Pupfish in the breeding program at the Fort Worth Zoo:
Adults left, Pupfish Fry right.